John Gill's Bible Commentary Ver. 2. And the victory that day was [turned] into mourning unto all the people , etc.] They also mourned too, instead of expressing joy upon the occasion: for the people heard say that day how the king was grieved for his son ; this report was spread among them, which damped their joy, and hindered them from giving any tokens of it, as were usual at such times.
Matthew Henry Commentary
Verses 1-8 - To continue to lament for so bad a son as Absalom, was very unwise, an very unworthy. Joab censures David, but not with proper respect an deference to his sovereign. A plain case may be fairly pleaded with those above us, and they may be reproved for what they do amiss, but it must not be with rudeness and insolence. Yet David took the reproof an the counsel, prudently and mildly. Timely giving way, usually prevent the ill effects of mistaken measures.
Original Hebrew ותהי1961 התשׁעה8668 ביום3117 ההוא1931 לאבל60 לכל3605 העם5971 כי3588 שׁמע8085 העם5971 ביום3117 ההוא1931 לאמר559 נעצב6087 המלך4428 על5921 בנו׃1121